It's not the first time a big Internet company has co-opted Android: Amazon.com Inc. has gone much further with its Kindle Fire tablets. They run a version of Android that strips out all Google services, replacing them with Amazon's equivalents. Barnes & Noble Inc. does the same thing with its Nook tablets. These devices lie outside the Google system, whereas phones running Facebook Home still come with Google apps such as Maps and the Play Store for music, movies and applications.

The Play Store has many examples of downloadable applications that modify the Android home screen — so-called "launchers." Home, however, represents the first time a major Internet company and Google competitor has created a downloadable launcher.

J.P. Morgan analyst Doug Anmuth said Home may increase the pressure on Google to find ways to get people to spend more time on its Plus social network, which so far hasn't been as magnetic as Facebook's hangout. Anmuth also believes the communication tools built into Home could decrease usage of Google's Gmail and Gchat services.

But Zuckerberg said the app will help Google.

"I think this is really good for Android," Zuckerberg told the audience at the launch event in Menlo Park, Calif. Developers do their best work on the iPhone first, but with Home, Facebook is putting Android first. If consumers want the Facebook Home experience, they'll have to get an Android phone.

In a statement, Google seemed to agree. "This latest device demonstrates the openness and flexibility that has made Android so popular," it said.

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AP Technology Writers Barbara Ortutay in New York and Michael Liedtke in Menlo Park, Calif., contributed to this report.